﻿using System.ComponentModel;
using System.Globalization;

namespace JenealehiKedelyuneaga;

/// <include file="../../../docs/Microsoft.Maui.Controls.Shapes/PathFigureCollectionConverter.xml" path="Type[@FullName='Microsoft.Maui.Controls.Shapes.PathFigureCollectionConverter']/Docs/*" />
public class PathFigureCollectionConverterNew : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        => sourceType == typeof(string);

    public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        => false;

    const bool AllowSign = true;
    const bool AllowComma = true;



    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        var strValue = value?.ToString();
        PathFigureCollection pathFigureCollection = new PathFigureCollection();

        ParseStringToPathFigureCollection(pathFigureCollection, strValue);

        return pathFigureCollection;
    }

    /// <include file="../../../docs/Microsoft.Maui.Controls.Shapes/PathFigureCollectionConverter.xml" path="//Member[@MemberName='ParseStringToPathFigureCollection']/Docs/*" />
    public static void ParseStringToPathFigureCollection(PathFigureCollection pathFigureCollection, string pathString)
    {
        bool figureStarted = default;
        string currentPathString = default;
        int pathLength = default;
        int currentIndex = default;
        Point lastStart = default;
        Point lastPoint = default;
        Point secondLastPoint = default;
        char token = default;

        if (pathString != null)
        {
            int curIndex = 0;

            while ((curIndex < pathString.Length) && char.IsWhiteSpace(pathString, curIndex))
            {
                curIndex++;
            }

            if (curIndex < pathString.Length)
            {
                if (pathString[curIndex] == 'F')
                {
                    curIndex++;

                    while ((curIndex < pathString.Length) && char.IsWhiteSpace(pathString, curIndex))
                    {
                        curIndex++;
                    }

                    // If we ran out of text, this is an error, because 'F' cannot be specified without 0 or 1
                    // Also, if the next token isn't 0 or 1, this too is illegal
                    if ((curIndex == pathString.Length) ||
                        ((pathString[curIndex] != '0') &&
                         (pathString[curIndex] != '1')))
                    {
                        throw new FormatException("IllegalToken");
                    }

                    // Increment curIndex to point to the next char
                    curIndex++;
                }
            }

            ParseToPathFigureCollection(pathFigureCollection, pathString, curIndex);
        }

        void ParseToPathFigureCollection(PathFigureCollection pathFigureCollection, string pathString, int startIndex)
        {
            PathFigure pathFigure = null;

            currentPathString = pathString;
            pathLength = pathString.Length;
            currentIndex = startIndex;

            secondLastPoint = new Point(0, 0);
            lastPoint = new Point(0, 0);
            lastStart = new Point(0, 0);

            figureStarted = false;

            bool first = true;

            char last_cmd = ' ';

            while (ReadToken()) // Empty path is allowed in XAML
            {
                char cmd = token;

                if (first)
                {
                    if ((cmd != 'M') && (cmd != 'm'))  // Path starts with M|m
                    {
                        ThrowBadToken();
                    }

                    first = false;
                }

                switch (cmd)
                {
                    case 'm':
                    case 'M':
                        // XAML allows multiple points after M/m
                        lastPoint = ReadPoint(cmd, !AllowComma);

                        pathFigure = new PathFigure
                        {
                            StartPoint = lastPoint
                        };
                        pathFigureCollection.Add(pathFigure);

                        figureStarted = true;
                        lastStart = lastPoint;
                        last_cmd = 'M';

                        while (IsNumber(AllowComma))
                        {
                            lastPoint = ReadPoint(cmd, !AllowComma);

                            LineSegment lineSegment = new LineSegment
                            {
                                Point = lastPoint
                            };
                            pathFigure.Segments.Add(lineSegment);

                            last_cmd = 'L';
                        }
                        break;

                    case 'l':
                    case 'L':
                    case 'h':
                    case 'H':
                    case 'v':
                    case 'V':
                        EnsureFigure();

                        do
                        {
                            switch (cmd)
                            {
                                case 'l':
                                    lastPoint = ReadPoint(cmd, !AllowComma);
                                    break;
                                case 'L':
                                    lastPoint = ReadPoint(cmd, !AllowComma);
                                    break;
                                case 'h':
                                    lastPoint.X += ReadNumber(!AllowComma);
                                    break;
                                case 'H':
                                    lastPoint.X = ReadNumber(!AllowComma);
                                    break;
                                case 'v':
                                    lastPoint.Y += ReadNumber(!AllowComma);
                                    break;
                                case 'V':
                                    lastPoint.Y = ReadNumber(!AllowComma);
                                    break;
                            }

                            pathFigure.Segments.Add(new LineSegment
                            {
                                Point = lastPoint
                            });
                        }
                        while (IsNumber(AllowComma));

                        last_cmd = 'L';
                        break;

                    case 'c':
                    case 'C': // Cubic Bezier
                    case 's':
                    case 'S': // Smooth cublic Bezier
                        EnsureFigure();

                        do
                        {
                            Point p;

                            if ((cmd == 's') || (cmd == 'S'))
                            {
                                if (last_cmd == 'C')
                                {
                                    p = Reflect();
                                }
                                else
                                {
                                    p = lastPoint;
                                }

                                secondLastPoint = ReadPoint(cmd, !AllowComma);
                            }
                            else
                            {
                                p = ReadPoint(cmd, !AllowComma);

                                secondLastPoint = ReadPoint(cmd, AllowComma);
                            }

                            lastPoint = ReadPoint(cmd, AllowComma);

                            BezierSegment bezierSegment = new BezierSegment
                            {
                                Point1 = p,
                                Point2 = secondLastPoint,
                                Point3 = lastPoint
                            };

                            pathFigure.Segments.Add(bezierSegment);

                            last_cmd = 'C';
                        }
                        while (IsNumber(AllowComma));

                        break;

                    case 'q':
                    case 'Q': // Quadratic Bezier
                    case 't':
                    case 'T': // Smooth quadratic Bezier
                        EnsureFigure();

                        do
                        {
                            if ((cmd == 't') || (cmd == 'T'))
                            {
                                if (last_cmd == 'Q')
                                {
                                    secondLastPoint = Reflect();
                                }
                                else
                                {
                                    secondLastPoint = lastPoint;
                                }

                                lastPoint = ReadPoint(cmd, !AllowComma);
                            }
                            else
                            {
                                secondLastPoint = ReadPoint(cmd, !AllowComma);
                                lastPoint = ReadPoint(cmd, AllowComma);
                            }

                            QuadraticBezierSegment quadraticBezierSegment = new QuadraticBezierSegment
                            {
                                Point1 = secondLastPoint,
                                Point2 = lastPoint
                            };

                            pathFigure.Segments.Add(quadraticBezierSegment);

                            last_cmd = 'Q';
                        }
                        while (IsNumber(AllowComma));

                        break;

                    case 'a':
                    case 'A':
                        EnsureFigure();

                        do
                        {
                            // A 3,4 5, 0, 0, 6,7
                            double w = ReadNumber(!AllowComma);
                            double h = ReadNumber(AllowComma);
                            double rotation = ReadNumber(AllowComma);
                            bool large = ReadBool();
                            bool sweep = ReadBool();

                            lastPoint = ReadPoint(cmd, AllowComma);

                            ArcSegment arcSegment = new ArcSegment
                            {
                                Size = new Size(w, h),
                                RotationAngle = rotation,
                                IsLargeArc = large,
                                SweepDirection = sweep ? SweepDirection.Clockwise : SweepDirection.CounterClockwise,
                                Point = lastPoint
                            };

                            pathFigure.Segments.Add(arcSegment);
                        }
                        while (IsNumber(AllowComma));

                        last_cmd = 'A';
                        break;

                    case 'z':
                    case 'Z':
                        EnsureFigure();
                        pathFigure.IsClosed = true;
                        figureStarted = false;
                        last_cmd = 'Z';

                        lastPoint = lastStart; // Set reference point to be first point of current figure
                        break;

                    default:
                        ThrowBadToken();
                        break;
                }
            }
        }

        void EnsureFigure()
        {
            if (!figureStarted)
                figureStarted = true;
        }

        Point Reflect()
        {
            return new Point(
                2 * lastPoint.X - secondLastPoint.X,
                2 * lastPoint.Y - secondLastPoint.Y);
        }






        bool More()
        {
            return currentIndex < pathLength;
        }

        bool SkipWhiteSpace(bool allowComma)
        {
            bool commaMet = false;

            while (More())
            {
                char ch = currentPathString[currentIndex];

                switch (ch)
                {
                    case ' ':
                    case '\n':
                    case '\r':
                    case '\t':
                        break;

                    case ',':
                        if (allowComma)
                        {
                            commaMet = true;
                            allowComma = false; // One comma only
                        }
                        else
                        {
                            ThrowBadToken();
                        }
                        break;

                    default:
                        // Avoid calling IsWhiteSpace for ch in (' ' .. 'z']
                        if (((ch > ' ') && (ch <= 'z')) || !char.IsWhiteSpace(ch))
                        {
                            return commaMet;
                        }
                        break;
                }

                currentIndex++;
            }

            return commaMet;
        }

        bool ReadBool()
        {
            SkipWhiteSpace(AllowComma);

            if (More())
            {
                token = currentPathString[currentIndex++];

                if (token == '0')
                {
                    return false;
                }
                else if (token == '1')
                {
                    return true;
                }
            }

            ThrowBadToken();

            return false;
        }

        bool ReadToken()
        {
            SkipWhiteSpace(!AllowComma);

            // Check for end of string
            if (More())
            {
                token = currentPathString[currentIndex++];

                return true;
            }
            else
            {
                return false;
            }
        }

        void ThrowBadToken()
        {
            throw new FormatException(string.Format("UnexpectedToken \"{0}\" into {1}", currentPathString, currentIndex - 1));
        }

        Point ReadPoint(char cmd, bool allowcomma)
        {
            double x = ReadNumber(allowcomma);
            double y = ReadNumber(AllowComma);

            if (cmd >= 'a') // 'A' < 'a'. lower case for relative
            {
                x += lastPoint.X;
                y += lastPoint.Y;
            }

            return new Point(x, y);
        }

        bool IsNumber(bool allowComma)
        {
            bool commaMet = SkipWhiteSpace(allowComma);

            if (More())
            {
                token = currentPathString[currentIndex];

                // Valid start of a number
                if ((token == '.') || (token == '-') || (token == '+') || ((token >= '0') && (token <= '9'))
                    || (token == 'I')  // Infinity
                    || (token == 'N')) // NaN
                {
                    return true;
                }
            }

            if (commaMet) // Only allowed between numbers
            {
                ThrowBadToken();
            }

            return false;
        }

        double ReadNumber(bool allowComma)
        {
            if (!IsNumber(allowComma))
            {
                ThrowBadToken();
            }

            bool simple = true;
            int start = currentIndex;

            // Allow for a sign
            // 
            // There are numbers that cannot be preceded with a sign, for instance, -NaN, but it's
            // fine to ignore that at this point, since the CLR parser will catch this later.
            if (More() && ((currentPathString[currentIndex] == '-') || currentPathString[currentIndex] == '+'))
            {
                currentIndex++;
            }

            // Check for Infinity (or -Infinity).
            if (More() && (currentPathString[currentIndex] == 'I'))
            {
                // Don't bother reading the characters, as the CLR parser will
                // do this for us later.
                currentIndex = Math.Min(currentIndex + 8, pathLength); // "Infinity" has 8 characters
                simple = false;
            }
            // Check for NaN
            else if (More() && (currentPathString[currentIndex] == 'N'))
            {
                //
                // Don't bother reading the characters, as the CLR parser will
                // do this for us later.
                //
                currentIndex = Math.Min(currentIndex + 3, pathLength); // "NaN" has 3 characters
                simple = false;
            }
            else
            {
                SkipDigits(!AllowSign);

                // Optional period, followed by more digits
                if (More() && (currentPathString[currentIndex] == '.'))
                {
                    simple = false;
                    currentIndex++;
                    SkipDigits(!AllowSign);
                }

                // Exponent
                if (More() && ((currentPathString[currentIndex] == 'E') || (currentPathString[currentIndex] == 'e')))
                {
                    simple = false;
                    currentIndex++;
                    SkipDigits(AllowSign);
                }
            }

            if (simple && (currentIndex <= (start + 8))) // 32-bit integer
            {
                int sign = 1;

                if (currentPathString[start] == '+')
                {
                    start++;
                }
                else if (currentPathString[start] == '-')
                {
                    start++;
                    sign = -1;
                }

                int value = 0;

                while (start < currentIndex)
                {
                    value = value * 10 + (currentPathString[start] - '0');
                    start++;
                }

                return value * sign;
            }
            else
            {
                string subString = currentPathString.Substring(start, currentIndex - start);

                try
                {
                    return Convert.ToDouble(subString, CultureInfo.InvariantCulture);
                }
                catch (FormatException)
                {
                    throw new FormatException(string.Format("UnexpectedToken \"{0}\" into {1}", start, currentPathString));
                }
            }
        }

        void SkipDigits(bool signAllowed)
        {
            // Allow for a sign
            if (signAllowed && More() && ((currentPathString[currentIndex] == '-') || currentPathString[currentIndex] == '+'))
            {
                currentIndex++;
            }

            while (More() && (currentPathString[currentIndex] >= '0') && (currentPathString[currentIndex] <= '9'))
            {
                currentIndex++;
            }
        }
    }


    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        => throw new NotSupportedException();
}